1. Field of the Invention
The present invention generally relates to data retrieval systems, and more particularly to a data retrieval system for retrieving at high speed a relational table in a relational database divided into parts of which form data.
2. Description of the Related Art
In a terminal such as work station, a data retrieval is made in an interactive mode in which an operator monitors a display screen of the terminal when retrieving a relational table of a relational database. As a result, the relational table is displayed on the display screen. It is desirable that the relational table can be retrieved at a high speed to improve efficiency.
In a conventional relational database, a table managing part which manages table items of the relational table and an item data part which manages specific numerical data for the table items are provided independently. In other words, as shown in FIG. 1, the table managing part is managed in file A, and the item data part is managed in file B which is independent of the file A.
But in the conventional relational database, the numerical data which are managed by the item data part are simply an enumeration of numerical data, and the numerical data have specific meanings only when combined with the table items of the table managing part in a memory as indicated by C in FIG. 1. For this reason, even when retrieving and displaying a portion of the relational table, it is first necessary in the conventional relational database to develop, or create, in the memory all of the table items managed by the table managing part and all of the numerical data managed by the item data part, that is, the entire relational table must be produced, before actually extracting the portion of the relational table which is to be displayed. However, developing the entire relational table in the memory takes time. As a result, the conventional relational database suffers from a problem in that it takes time to retrieve even a portion of the relational table.